Lytic transglycosylases LtgA and LtgD perform distinct roles in remodeling, recycling and releasing peptidoglycan in Neisseria gonorrhoeae.

Abstract

Neisseria gonorrhoeae releases peptidoglycan (PG) fragments during infection that provoke a large inflammatory response and, in pelvic inflammatory disease, this response leads to the death and sloughing of ciliated cells of the Fallopian tube. We characterized the biochemical functions and localization of two enzymes responsible for the release of proinflammatory PG fragments. The putative lytic transglycosylases LtgA and LtgD were shown to create the 1,6-anhydromuramyl moieties, and both enzymes were able to digest a small, synthetic tetrasaccharide dipeptide PG fragment into the cognate 1,6-anhydromuramyl-containing reaction products. Degradation of tetrasaccharide PG fragments by LtgA is the first demonstration of a family 1 lytic transglycosylase exhibiting this activity. Pulse-chase experiments in gonococci demonstrated that LtgA produces a larger amount of PG fragments than LtgD, and a vast majority of these fragments are recycled. In contrast, LtgD was necessary for wild-type levels of PG precursor incorporation and produced fragments predominantly released from the cell. Additionally, super-resolution microscopy established that LtgA localizes to the septum, whereas LtgD is localized around the cell. This investigation suggests a model where LtgD produces PG monomers in such a way that these fragments are released, whereas LtgA creates fragments that are mostly taken into the cytoplasm for recycling.

• Authors: Ryan E Schaub, Yolande A Chan, Mijoon Lee, Dusan Hesek, Shahriar Mobashery, Joseph P Dillard
• Journal: Molecular microbiology (Mol Microbiol) Vol. 102 Issue 5 Pg. 865-881 (12 2016) ISSN: 1365-2958 [Electronic] England
• PMID: 27608412 (Publication Type: Journal Article)
• Copyright: © 2016 John Wiley & Sons Ltd.

Chemical References

• Bacterial Proteins
• Peptidoglycan
• Peptidoglycan Glycosyltransferase

Topics

• Bacterial Proteins (genetics, metabolism)
• Cell Wall (enzymology, metabolism)
• Mutation
• Neisseria gonorrhoeae (enzymology, genetics, metabolism)
• Peptidoglycan (metabolism)
• Peptidoglycan Glycosyltransferase (genetics, metabolism)